In connection with the recovery of hydrocarbons from the earth, wellbores are generally drilled using a variety of different methods and equipment. According to one common method, a roller cone bit or fixed cutter bit is rotated against the subsurface formation to form the well bore. The rotating bit is suspended in the well bore by a tubular drill string. Drilling fluid is pumped through the drill string and discharged at or near the drill bit to assist in drilling operations. In some systems, the flow of drilling fluid through the drill string is altered by diverting a portion of the main flow and discharging the diverted portion from the drill string.